The Strange Physics Of Curling

February 20, 2018 by Adam Fabio 36 Comments

It turns out that curling involves some complex physics. [Destin] of Smarter Every Day has jumped in to find out why scientists on opposite sides of the Atlantic disagree about why curling stones curl.

If you’ve been watching the Olympics, you’ve probably seen some curling, the Scottish sport of competitively pushing stones on ice. As the name implies, curling stones don’t go straight. The thrower pushes them with a bit of rotation, and the stones curve in the direction they are rotating. This is exactly the opposite of what one would expect — try it yourself with an inverted drinking glass on a smooth table. The glass will curl opposite the direction of rotation. Clockwise spin will result in a curl to the left, counterclockwise in a curl to the right.

The cup makes sense when you think about the asymmetrical friction involved. The cup is slowing down, which means more pressure on the leading edge. The rotating leading edge pushes harder against the table and causes the cup to curl opposite the direction of rotation.

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This Boxing Bell Is A Trip

February 17, 2018 by Adam Fabio 8 Comments

[MeasuredWorkshop] wanted to know how a boxing bell mechanism worked. The best way to learn is by doing, so he jumped right in and built one! Boxing bells are a rare surviving example of the trip bell mechanism. Trip bells were used in schools and public buildings as fire alarms. They’ve since been replaced by modern electric systems.

The mechanical linkage behind the trip bell is a one-way lever. This is the arm you pull on. It has a hinged section which stays rigid when the arm is pulled down, but rotates away when the arm is released. [Measured Workshop] built the mechanics of his bell using rather basic tools. The brunt of the work was handled by an angle grinder and a drill press.

The sounder for this boxing bell came from an old school bell. The industrial grey paint was chemically stripped, and the metal cleaned up for a nice brushed finish. The metal stands out nicely against the wood board [Measured Workshop] used as a base.

The finished product looks and sounds the part – now he just has to find a boxing gym in need of a bell!

We’re really becoming fond of the “wordless workshop” style videos that have been popping up on YouTube. [Jimmy DiResta] has been doing it for years, and relative newcomers [HandToolRescue] and [Measured Workshop] are both producing some great content!

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IBM 1401 Runs FORTRAN II Once More

February 11, 2018 by Adam Fabio 41 Comments

The IBM 1401 is undeniably a classic computer. One of IBM’s most “affordable” mainframes, it ruled the small business computing world of the 1960’s. Unfortunately, computers aren’t often thought of as treasured heirlooms, only a handful of these machines survive today. The computer history museum has two machines. One from Germany, and the other recovered from a basement in Connecticut back in 2008. [CuriousMarc] and the rest of the team at the museum have been working diligently to restore the 1401, and they’ve hit quite a milestone — They can now compile and run FORTRAN II code.

Getting the 1401 to run FORTRAN II itself is quite an accomplishment. The hardest part was dealing with the 729 vacuum column tape drives. The team spent years building a hardware emulator which takes the place of the real drives. The emulator is driven by an old PC running windows. Tape images are stored as files, which can be loaded, rewound, and run just like a real 729.

Emulators are great, but [Mark] and his team wanted this to run on the real hardware. They first had to re-create a FORTRAN compiler tape. They ran a tape copier program on the 1401, then loaded an image of the compiler on their emulator. The computer dutifully copied the image to a real tape drive.

The team also needed a punched card deck of FORTRAN source code to compile and run. The first example in the FORTRAN manual is a Hilbert Matrix program. The team could have used a keypunch machine to punch the cards for the program, but that is a painstaking and error-prone process. One mistake, and they would have to re-punch an entire card — much like using an old typewriter with no White-Out or correction ribbon. Instead, they typed the source into a PC, then converted the file to a tape image. A small program instructed the 1401 to punch the source code out on cards for them.

At the moment of truth, shown first in the video, the 1401 reads FORTRAN II from tape, pulls in the source code from punched cards, compiles, runs, and then prints the result on its line printer. All the original hardware singing along just like it did in 1959.

If you haven’t been to the Computer History Museum yet, check it out! It’s also the site of Vintage Computing Festival West.

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Flexiphone Rises From The Ashes Of Broken Instruments

February 2, 2018 by Adam Fabio 7 Comments

The mechanics of an old Rhodes Piano, and a set of chromatic saucer bells rescued from a reed organ. What do these two things have to do with each other? If you’re [Measured Workshop], they are the makings of a new instrument. The Flexiphone is a transposable instrument with a piano keyboard and interchangeable sound source.

The Rhodes is a great stage instrument. Unlike a piano with strings, it uses tines mounted above the key mechanism. It is also relatively compact for an analog instrument. This made it perfect as a donor for the Flexiphone’s keyboard. [Measured Workshop] cut they mechanism down to 30 keys, just under 2 octaves. The key mechanism was also cleaned up and restored with new felt.

The sounding portion of the Flexiphone is a set of chromatic saucer bells. The bells are mounted on a felt covered threaded rod, which itself sits in a wood frame. The bell frame sits on top of the base in one of three slots. Each slot is a halftone transposed from the last. Simply moving the bells allows the player to transpose the entire instrument. The bells and their rod frame can also be completely removed and replaced with any other sound source.

The Flexiphone sounds great — sometimes. As [Measured Workshop] says, bells contain many harmonics. playing single or double notes sounds rather sweet, but chords can sometimes become a shrill assault on the ears. Still, it’s an awesome hack with plenty of potential for future mods.

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Travel In Style On An Electric Air Sled

February 1, 2018 by Adam Fabio 41 Comments

What do you do during the winter months in Ohio? Sledding of course! Sledding normally takes place on hills, but [Peter Sripol] is no slave to the terrain. He’s built an air sled to conquer the barren wastelands of unplowed parking lots. Air sleds aren’t as outlandish as you might think — the Soviet Union had decades of success with them.

The project starts with toboggan style plastic sled. [Peter] built a frame into the plastic using an aluminum square. The frame is used to support a motor pod at the back of the sled. The motor, of course, comes from his DIY electric plane project. Don’t worry — [Peter] didn’t cannibalize his plane. The plane’s motors are being upgraded, and this is one of the originals.

The motor itself is quite a beast. It’s a 150cc equivalent brushless outrunner motor from HobbyKing. It’s not cheap either at around $450 USD. The motor is controlled by an equally beefy brushless controller wired into a standard R/C car receiver. A pistol grip transmitter makes a great wireless throttle for the system.

Steering is a much more mechanical affair. The sled’s rudder is controlled much like that of an airplane. A steel cable pull-pull system is connected to a stick mounted in front of the pilot. The unreinforced styrofoam rudder turned out to be a weak point in the build — check out the video after the break to see the full story.

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Strumbot: The Guitar That Strums Itself

January 31, 2018 by Adam Fabio 13 Comments

[Clare] isn’t the most musically inclined person, but she can strum a guitar. Thanks to a little help from an Arduino, she doesn’t even have to do that.

She built the strumbot, which handles the strumming hand duties of playing the guitar. While [Claire] does believe in her strumbot, she didn’t want to drill holes in her guitar, so hot glue and double-sided foam tape were the order of the day.

The business end of the strumbot is a micro servo. The servo moves two chopsticks and draws the pick across the strings. The tiny servo surprisingly does a great job getting the strings ringing. The only downside is the noise from the plastic gears when it’s really rocking out.

Strumbot’s user interface is a 3D-printed case with three buttons and three LEDs. Each button activates a different strum pattern in the Arduino’s programming. The LEDs indicate the currently active pattern. Everything is powered by a USB power pack, making this a self-contained hack.

[Clare] was able to code up some complex strum patterns, but the strumbot is still a bit limited in that it only holds three patterns. It’s good enough for her rendition of “Call Me Maybe”, which you can see in the video after the break. Sure, this is a simple project, not nearly as complex as some of the robotic guitar mods we’ve seen in the past. Still, it’s just the ticket for a fun evening or weekend project – especially if you’re introducing the Arduino to young coders. Music, hacking, and modding – what more could you ask for?

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Chasing The Electron Beam At 380,000 FPS

January 29, 2018 by Adam Fabio 20 Comments

Analog TV is dead, but that doesn’t make it any less awesome. [Gavin and Dan], aka The Slow Mo Guys recently posted a video about television screens. Since they have some incredible high-speed cameras at their disposal, we get to see the screens being drawn, both on CRT and more modern LCD televisions.

Now we all know that CRTs draw one pixel at a time, drawing from left to right, top to bottom. You can capture this with a regular still camera at a high shutter speed. The light from a TV screen comes from a phosphor coating painted on the inside of the glass screen. Phosphor glows for some time after it is excited, but how long exactly? [Gavin and Dan’s] high framerate camera let them observe the phosphor staying illuminated for only about 6 lines before it started to fade away. You can see this effect at a relatively mundane 2500 FPS.

Cranking things up to 380,117 FPS, the highest speed ever recorded by the duo, we see even more amazing results. Even at this speed, quite a few “pixels” are drawn each frame. [Gavin] illustrates that by showing how Super Mario’s mustache is drawn in less than one frame of slow-mo footage. You would have to go several times faster to actually freeze the electron beam. We think it’s amazing that such high-speed analog electronics were invented and perfected decades ago.

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